1. Field of the Invention
The present invention relates to an electromagnetic shielding film, a plasma display panel (PDP) filter using the electromagnetic shielding film, a PDP device including the electromagnetic shielding film, and a method of manufacturing the electromagnetic shielding film. More particularly, the present invention relates to an electromagnetic shielding film having a high refractive index in a visible light region, which can improve brightness and image quality by blackening not only a portion of the shielding film facing a user's side but also a portion opposite to the user's side, a method of manufacturing the electromagnetic shielding film, a PDP filter using the electromagnetic shielding film, and a PDP device including the electromagnetic shielding film.
2. Description of the Related Art
As modern society becomes more information-oriented, photoelectronic devices advancing and being more widely used. In particular, image display devices are widely used in a variety of applications, including TV screens, monitors of personal computers, etc. Wide screens and a thin build have become the mainstream technology for high performance image display devices.
Plasma display panels are gaining popularity as a next-generation display device to replace the CRT because of advantages in thinness, and that a big screen can be readily fabricated with a plurality of units. A PDP device includes a plasma display panel on which an image is displayed using a gas discharge phenomenon, and exhibits superior display capabilities, including high display capacity, high brightness, high contrast, clear latent image, and a wide viewing angle.
In a PDP device, when a direct current (DC) or alternating current (AC) voltage is applied to electrodes, a discharge of gas plasma is created, resulting in the emission of ultraviolet (UV) light. The UV emission excites adjacent phosphor materials, resulting in electromagnetic emission of visible light.
Despite the above advantages, PDPs have several problems associated with driving characteristics, including an increase in electromagnetic wave radiation, near-infrared emission, and phosphor surface reflection, and an obscured color purity due to orange light emitted from helium (He) or xenon (Xe) used as a sealing gas.
The electromagnetic wave and near-infrared ray generated in PDPs may adversely affect human bodies and cause malfunction of precision machines such as wireless telephones or remote controllers. Thus, in order to make use of such PDPs, there is a desire to reduce the electromagnetic wave and near-infrared rays emitted from the PDPs. In this respect, various PDP filters have been used for the purposes of, for example, shielding electromagnetic waves or near-infrared rays emitted from the PDPs, reducing reflection of light and/or enhancing color purity. Various PDP filters having an electromagnetic wave shielding function, a near-infrared rays shielding function, an antireflection function, and/or a color purity enhancing function, can be formed together with the PDPs.
A plasma display panel device includes a panel assembly that has a discharge cell in which gas discharge occurs and a PDP filter that shields electromagnetic waves and near-infrared rays.
The PDP filter, which is mounted on the entire surface of the panel assembly, should interfere as little as possible with transparency.
In a PDP device, an electric current flowing between a driving circuit and an alternating current (AC) electrode and a high voltage between electrodes used for plasma discharge are the main causes of electromagnetic waves. The electromagnetic waves generated by such causes are mainly in the frequency band of 30-200 MHz. Generally, a transparent conductive film or a conductive mesh that maintains a high visible light transmittance and a low refractive index in a visible light region is used as an electromagnetic shielding layer for shielding the generated electromagnetic waves.
An electromagnetic shielding layer made of a conductive mesh exhibits a superior electromagnetic shielding capability. An electromagnetic shielding layer made of a transparent conductive film such as an Indium Tin Oxide (ITO) film generally takes the form of a multi-layered thin film in which a metal thin film and a high refractive index transparent thin film are alternately coated. A main element of the metal thin film is silver (Ag) or an alloy of silver (Ag).
Hereinafter, a conventional method of manufacturing an electromagnetic shielding film including a conductive mesh will be described with reference to FIGS. 1A through 1C. FIGS. 1A through 1C are sectional views of sequential processing steps for explaining the conventional method of manufacturing an electromagnetic shielding film.
As shown in FIG. 1A, a metal thin film 30 is attached to a transparent substrate 10 using an adhesive 20 having appropriate adhesion strength through lamination. The transparent substrate 10 is generally a polyethylene terephthalate (PET) film. As shown in FIG. 1B, a photoresist pattern 40 is formed by coating a photoresist on the metal thin film 30 and patterning the photoresist using a photolithographic process (an exposure process and a development process). As shown in FIG. 1C, an electromagnetic shielding film pattern 32 is formed by etching the metal thin film 30 using the photoresist pattern 40 as an etching mask. After the photoresist pattern 40 used as the etching mask is removed, the electromagnetic shielding film pattern 32 on the transparent substrate 10 is blackened. The electromagnetic shielding film pattern 32 is generally made of a metal thin film having high electromagnetic shielding performance. However, when the electromagnetic shielding film pattern 32 is formed of a metal thin film, the inherent high refractive index of the metal thin film in the visible light region poses a problem. In particular, copper, which is widely used as the electromagnetic shielding film pattern 32, has a refractive index of 60% or more in the visible light region. Thus, when a PDP filter including the electromagnetic shielding film pattern 32 formed of copper is used on a PDP device, the brightness of the PDP device drops significantly. To reduce the refractive index of a metal, the electromagnetic shielding film pattern 32 is blackened. Referring to FIG. 1C, three faces of the conventional electromagnetic shielding film pattern 32, except for a face opposite to the transparent substrate 10, are blackened. In general, blackened portions of the electromagnetic shielding film pattern 32 face a user's (or viewer's) side of the PDP device. Thus, the refractive index of the PDP device in the visible light region is reduced from the viewpoint of the viewer.
However, since a portion of the electromagnetic shielding film pattern 32 facing the panel assembly's side is not blackened, the PDP device cannot obtain high brightness. In other words, light generated by the panel assembly of the PDP device is reflected from the electromagnetic shielding film pattern 32 and then enters the panel assembly, resulting in light superposition. As a result, the brightness of the PDP device drops, degrading image display capability.
Another conventional technique regarding a PDP filter having an electromagnetic shielding film pattern is disclosed in Japanese Patent Application No. Hei 11-119675 filed on Oct. 16, 1997, which is directed to a method of manufacturing an electromagnetic shielding plate. In the electromagnetic shielding plate, only a face opposite to the viewer's side is blackened. As a result, like the prior art shown in FIGS. 1A through 1C, light generated by a panel assembly is reflected from the electromagnetic shielding plate and then enters the panel assembly, resulting in degradation of the brightness and performance of a PDP device.